Explosive cartridge

ABSTRACT

An explosive cartridge comprising a container having therein a slurry of high explosive charge, a cast booster charge and a loop of detonating cord associated with the cast booster charge and extending outside the container, the cartridge being provided with means to maintain the cast booster charge in contact with the slurry explosive charge upon application of tension on the loop of detonating cord.

United States" Patent Kern [54] EXPLOSIVE CARTRIDGE [72] inventor: Forrest L. Kern, Allentown, Pa.

[73] Assignee: Commercial Solvents Corporation [22] Filed: July 29, 1970 [2i] Appl. No.: 59,318

[52] US. Cl. ..l02/24 [51] Int. Cl. ..F42b 3/00 [58] H Field of Search l02/22-24, 27

[56] References Cited UNITED STATES PATENTS 3,256,814 6/1966 Kruppenbach et al......l02/24 [4 1 Sept. 19, 1972 Primary Examiner-Verlin R. Pendegrass Attorney-John W. Behringer, Eugene L. Bernard, Martin J. Brown, James N. Dresser, W. Brown Morton, Jr., John T. Roberts, Malcolm L. Sutherland and Morton, Bernard, Brown, Roberts 8L Sutherland [5 7 1 ABSTRACT An explosive cartridge comprising a container having therein a slurry of high explosive charge, a cast booster charge and a loop of detonating cord associated with the cast booster charge and extending outside the container, the cartridge being provided with means to maintain the cast booster charge in contact with the slurry explosive charge upon application of tension on the loop of detonating cord.

1 Claim, 3 Drawing Figures PATENTED SEP 1 9 I972 I\'\'E\'TOR.

FORREST L. KERN BYW 5, 7 M

EXPLOSIVE CARTRIDGE This invention relates to an explosive cartridge useful in mining, quarrying and oil recovery operations wherein explosives are lowered into drill holes. Such operations are described in US. Pat. No. 3,256,814, issued June 21, 1966 to Kruppenbach et al. as are explosive cartridges used therein.

As described in that patent, in common practice a plurality of explosive cartridges are loaded into a drill hole tied to a common fuse that extends the length of the drill hole. During the loading operation and in distended holes, tension is applied to the connection between the detonating fuse and the explosive cartridge such that occasionally the explosive cartridge misflres. The explosive cartridge of this invention is designed to obviate misfirings in the drill hole.

STATEMENT OF INVENTION The explosive cartridge of this invention comprises a container having therein a slurry high explosive charge, a cast booster charge and detonating cord.

The slurry explosive charge is confined in the closed lower end of an outer flexible tube. A cast booster charge adapted to receive a loop of detonating cord, and having a closed loop of detonating cord passing through the booster charge and extending upwardly therefrom, is confined in an inner flexible tube.

The inner flexible tube containing the cast booster charge and the loop of detonating cord is positioned within the outer flexible tube at least partially submerged in the slurry high explosive charge.

A tie closure to close the upper end of the outer flexible tube and form the container is positioned near the upper end of the outer flexible tube and above the booster charge and is drawn tightly around the outer flexible tube, the inner flexible tube and the detonating cord extending upwardly from the booster charge such that the upper end of the loop of detonating cord extends through the tie closure and outside the container.

A rigid spacing means surrounding the detonating cord is positioned within the outer flexible tube below the tie closure and above the booster charge, the rigid spacing means being dimensioned to maintain the cast booster charge at least partially submerged in the slurry explosive charge during periods of tension applied to the ring-shaped fuse holder.

A ring-shaped fuse holder surrounds the upper end of the loop of detonating cord and is dimensioned to receive the detonating fuse.

A preferred embodiment of the explosive cartridge of this invention is shown in the accompanying drawings wherein:

FIG. I is a longitudinal section of an explosive cartridge of the invention showing the spacing means positioned between the inner and outer flexible tubes;

FIG. 2 is a longitudinal section of an explosive cartridge of the invention showing the spacing means positioned within the inner flexible tube; and

FIG. 3 is a longitudinal cross-section of a distended drill or bore hole showing a train of the explosive cartridges of the invention tied to a detonating fuse downline.

Referring to FIG. 1, the explosive cartridge comprises a cardboard protective sheath 1, an outer flexible tube 4 containing a slurry explosive charge 5, and an inner flexible tube 6 containing a cast booster charge 7.

Cast booster charge 7 is of the type described in US Pat. No. 3,359,902 issued Dec. 26, 1967 to Minnick et a1. having passages therethrough adapted to receive a loop of detonating cord. Twin loops of detonating cord 3 pass through cast booster charge 7 and extend upwardly therefrom. Wire tie closure 10 is drawn tightly around outer flexible tube 4, inner flexible tube 6 and detonating cord 3. Surrounding the upper end of the loops of detonating cord 3 are slip-rings l4.

Positioned between outer flexible tube 4 and inner flexible tube 6 and surrounding detonating cord 3 is rigid spacing means 8 in the form of a section of rigid plastic pipe. Spacing means 8 separates outer flexible tube 4 and inner flexible tube 6 and, bearing against the respective tube surfaces, maintains cast booster charge 7 at least partially submerged in slurry explosive charge 5, i.e., below level 5 of slurry explosive charge 5.

FIG. 2 differs from FIG. 1 in that rigid spacing means 8 is positioned within inner flexible tube 6. In this embodiment, spacing means 8 bears against the inner surface flexible tube 6 at one end and against cast booster charge 7 at the other end to maintain cast booster charge 7 at least partially submerged in slurry explosive 5.

FIG. 3 shows the effect of tension on the explosive cartridge when tied to and strung on a detonating fuse downline in a drill hole. Tension on slip-rings 14 tends to pull cast booster charge 7 out of contact with slurry explosive charge 5. Spacing means 8 maintains cast booster charge 7 at all times at least partially submerged in slurry explosive charge 5.

Slurry high explosive charge 5 can be of the relatively insensitive type conventionally employed, preferably a high explosive with a density greater than that of water and a detonating velocity of about 18,000 feet per second. As described in U. S. Pat. No. 3,256,814, any high explosive can be used, such as TNT sensitized ammonium nitrate type slurry high explosives, smokeless powder sensitized ammonium nitrate type slurry high explosives; nitrostarch sensitized ammonium nitrate type slurry high explosives; and nitrostarch sensitized ammonium nitrate type semisolid high explosives, nitrocarbonitrates, nitroglycerine dynamites, such as semigelatins, ammonia gelatins and ammonia dynamites. The density is not critical, but should exceed that of water by a sufficient amount to ensure that the primer will not float, and will preferably be at least 1.4. The detonating velocity will be sufficiently high to detonate the nitrocarbonitrate cartridges. This is known, and in the case of nitrocarbonitrate cartridges is usually at least 18,000 ft./sec.

Cast booster charge 7 can be of the type conventionally employed such as described in US. Pat No. 3,359,902. These are normally composed of cast Primacord-insensitive explosive material of high brisance, e.g., cast or pressed TNT, composition B (59% RDX, 40% TNT and 1% wax) or a mixture thereof, having imbedded therein, for example, tubular material fabricated from any of the Primacord-sensitive explosive materials presently available including pentaerythritol tetranitrate (PETN cyclotrimethylenetrinitramine (RDX tetranitromethylaniline (tetryl pentolite {5 0% PETN-50% TNT), etc. The cast booster may, however, be composed entirely of irimacord-sensitive explosive material such as, for example, pentolite.

Detonating cord 3 advantageously is Primacord.

Flexible tubes 4 and 6 can be fabricated from a flexible plastic such as polyethylene or polypropylene, and rigid spacing means 8 can be fabricated from a plastic such as polypropylene or polystyrene so long as wall thickness is sufficient to impart rigidity.

I claim:

1. An explosive package comprising a container having therein a slurry high explosive charge, a cast booster charge and detonating cord;

the slurry explosive charge being confined in the closed lower end of an outer flexible tube,

a cast booster charge being adapted to receive a loop of detonating cord, a closed loop of detonating cord passing through the booster charge and extending upwardly therefrom,

the cast booster charge and the loop of detonating charge extending therefrom being confined in an inner flexible tube,

the inner flexible tube containing the cast booster charge and the loop of detonating cord being positioned within the outer flexible tube at least partially submerged within the slurry high explosive charge,

a tie closure to close the upper end of the outer flexible tube and form the container, the tie closure being near the upper end of the outer flexible tube and above the booster charge and being drawn tightly around the outer flexible tube, the inner flexible tube and the detonating cord extending upwardly from the booster charge such that the upper end of the loop of detonating cord extends through the tie closure and outside the container,

rigid spacing means surrounding the detonating cord and positioned within the outer flexible tube below the tie closure and above the booster charge,

and a ring-shaped fuse holder surrounding the upper end of the loop of detonating cord and dimensioned to receive a detonating fuse,

the rigid spacing means being dimensioned to maintain the cast booster charge at least partially submerged in the slurry explosive charge during periods of tension applied to the ring-shaped fuse holder. 

